 /*******************************************************************************
  * Copyright (c) 2007 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  ******************************************************************************/

 package org.eclipse.ui.internal;

 import java.util.Collection ;

 import org.eclipse.core.expressions.IEvaluationContext;
 import org.eclipse.jface.viewers.ISelection;
 import org.eclipse.swt.widgets.Shell;
 import org.eclipse.ui.IEditorPart;
 import org.eclipse.ui.ISources;
 import org.eclipse.ui.IWorkbenchPart;
 import org.eclipse.ui.IWorkbenchSite;
 import org.eclipse.ui.IWorkbenchWindow;

 /**
  * Some common utilities for working with handlers and IEvaluationContexts in
  * Platform UI.
  * <p>
  * <b>Note</b>: this class should not be instantiated or extended by clients.
  * </p>
  * <p>
  * <strong>PROVISIONAL</strong>. This class or interface has been added as part
  * of a work in progress. There is a guarantee neither that this API will work
  * nor that it will remain the same. Please do not use this API without
  * consulting with the Platform/UI team.
  * </p>
  *
  * @since 3.3
  */
 public class InternalHandlerUtil {
     /**
      * Extract the variable.
      *
      * @param appContext
      * The application context
      * @param name
      * The variable name to extract.
      * @return The object from the application context, or <code>null</code>
      * if it could not be found.
      */
     public static Object getVariable(Object appContext, String name) {
         if (appContext instanceof IEvaluationContext) {
             return ((IEvaluationContext) appContext).getVariable(name);
         }
         return null;
     }

     /**
      * Return the active contexts.
      *
      * @param appContext
      * The execution appContext that contains the application context
      * @return a collection of String contextIds, or <code>null</code>.
      */
     public static Collection getActiveContexts(Object appContext) {
         Object o = getVariable(appContext, ISources.ACTIVE_CONTEXT_NAME);
         if (o instanceof Collection ) {
             return (Collection ) o;
         }
         return null;
     }

     /**
      * Return the active shell. Is not necessarily the active workbench window
      * shell.
      *
      * @param appContext
      * The execution appContext that contains the application context
      * @return the active shell, or <code>null</code>.
      */
     public static Shell getActiveShell(Object appContext) {
         Object o = getVariable(appContext, ISources.ACTIVE_SHELL_NAME);
         if (o instanceof Shell) {
             return (Shell) o;
         }
         return null;
     }

     /**
      * Return the active workbench window.
      *
      * @param appContext
      * The execution appContext that contains the application context
      * @return the active workbench window, or <code>null</code>.
      */
     public static IWorkbenchWindow getActiveWorkbenchWindow(Object appContext) {
         Object o = getVariable(appContext,
                 ISources.ACTIVE_WORKBENCH_WINDOW_NAME);
         if (o instanceof IWorkbenchWindow) {
             return (IWorkbenchWindow) o;
         }
         return null;
     }

     /**
      * Return the active editor.
      *
      * @param appContext
      * The execution appContext that contains the application context
      * @return the active editor, or <code>null</code>.
      */
     public static IEditorPart getActiveEditor(Object appContext) {
         Object o = getVariable(appContext, ISources.ACTIVE_EDITOR_NAME);
         if (o instanceof IEditorPart) {
             return (IEditorPart) o;
         }
         return null;
     }

     /**
      * Return the part id of the active editor.
      *
      * @param appContext
      * The execution appContext that contains the application context
      * @return the part id of the active editor, or <code>null</code>.
      */
     public static String getActiveEditorId(Object appContext) {
         Object o = getVariable(appContext, ISources.ACTIVE_EDITOR_ID_NAME);
         if (o instanceof String ) {
             return (String ) o;
         }
         return null;
     }

     /**
      * Return the active part.
      *
      * @param appContext
      * The execution appContext that contains the application context
      * @return the active part, or <code>null</code>.
      */
     public static IWorkbenchPart getActivePart(Object appContext) {
         Object o = getVariable(appContext, ISources.ACTIVE_PART_NAME);
         if (o instanceof IWorkbenchPart) {
             return (IWorkbenchPart) o;
         }
         return null;
     }

     /**
      * Return the part id of the active part.
      *
      * @param appContext
      * The execution appContext that contains the application context
      * @return the part id of the active part, or <code>null</code>.
      */
     public static String getActivePartId(Object appContext) {
         Object o = getVariable(appContext, ISources.ACTIVE_PART_ID_NAME);
         if (o instanceof String ) {
             return (String ) o;
         }
         return null;
     }

     /**
      * Return the active part site.
      *
      * @param appContext
      * The execution appContext that contains the application context
      * @return the active part site, or <code>null</code>.
      */
     public static IWorkbenchSite getActiveSite(Object appContext) {
         Object o = getVariable(appContext, ISources.ACTIVE_SITE_NAME);
         if (o instanceof IWorkbenchSite) {
             return (IWorkbenchSite) o;
         }
         return null;
     }

     /**
      * Return the current selection.
      *
      * @param appContext
      * The execution appContext that contains the application context
      * @return the current selection, or <code>null</code>.
      */
     public static ISelection getCurrentSelection(Object appContext) {
         Object o = getVariable(appContext,
                 ISources.ACTIVE_CURRENT_SELECTION_NAME);
         if (o instanceof ISelection) {
             return (ISelection) o;
         }
         return null;
     }
 }

